
The Cold War intensified in the 1950s, speed became the lifeblood of American aerial defense strategy. The U.S. Air Force, determined to outpace the Soviet threat, embarked on a quest for Mach 3 supremacy with the development of cutting-edge interceptors like the Republic XF-103 and the North American XF-108.

In 1949, the Air Force issued a request for a supersonic interceptor to counter high-flying Soviet nuclear bombers.

Designated the 1954 Interceptor project to mark the year it was to enter service, the Air Force received nine proposals, of which three were chosen for preliminary development: Convair with a design that later became the F-102 Delta Dagger, Lockheed with a plane that later became the F-104 Starfighter, and Republic Aircraft with the AP-57, later renamed the XF-103.

From several proposals, Republic Aircraft’s XF-103 emerged as a formidable contender with its vision of a ramjet-powered aircraft capable of reaching speeds of 2,600 miles per hour and an altitude of 80,000 feet.

This design was a leap beyond the subsonic F-86s and MiG-15s combat seen over Korea.

The XF-103, which was so advanced for its time that it looked more rocket than airplane, featured a dual propulsion system combining a turbojet for normal flight and a ramjet for that essential burst of speed to catch incoming bombers.

Despite its promise, Continuing delays and cost overruns halted the project, with the program being canceled on August 21, 1957.

Following the XF-103’s termination, focus shifted to North American Aviation’s XF-108, a long-range, two-man interceptor also capable of Mach 3 speeds.

The XF-108 aimed to fill the gaps in radar coverage with its cutting-edge Hughes AN/ASG-18 radar and Falcon missiles.

However, with a cost considered prohibitive and the rise of ICBMs, which shifted the nature of the nuclear threat, the XF-108 program was canceled in September 1959.

Though these projects were never fully realized, the drive for Mach 3 capability wasn’t futile.

Lockheed’s Skunk Works, led by the legendary Kelly Johnson, seized the opportunity to create the YF-12 based on the A-12 spy plane.

President Johnson announced the program’s existence on February 29, 1964, when he stated, “The United States has successfully developed and advanced experimental aircraft, the A-11, which has been tested in sustained flight at more than 2,000 mph and at altitudes above 70,000 feet”.

The “A-11” reference was used intentionally to mislead intelligence sources as the aircraft had recently been given the official designation of YF-12A.

This interceptor variant made its first flight on August 7, 1963, and went on to set speed and altitude records, though it too was eventually canceled with only three ever built.
Relevant articles:
– The F-103 Could Have Been America’s Mach 3 Ramjet Fighter, The National Interest
– 12A > Air Force Materiel Command > Article Display, Air Force Materiel Command (.mil)
– The F-108 Could Have Been America’s Mach 3 Cold War Super-Interceptor, The National Interest
– 103 Thunderwarrior Mach 3 superiority fighter project 1/72 scale, iModeler